DISCOVERIES IN ASTRONOMY. 



65 



SPECULATIONS SUGGESTED BY RECENT DISCOVERIES IN ASTRONOMY. 

 (Exiraclcd from Uie. private correspondence of a friend.) 



Have you seen the latest news from the sky ? Bessel, who, you 

 know, had the honor of first discovering the annual parallax of a fixed 

 star, has announced the discovery of orbitual motions in Procyon and 

 Sirius, or, to use his own words, "/Ae apparent motions of these two stars 

 are such as might he caused hy their revolutions ahout attractive but non- 

 luminous bodies not very remote from them respectively ^ In short, they 

 seem to form systems analogous to those of the binary stars, but w^ith 

 this peculiarity, that they have dark instead of bright partners, to which 

 they, of course, perform the friendly oflices of revolving suns ! 



Their orbits must, therefore, be highly inclined to the visual ray, else 

 in some parts of their courses they would inevitably be eclipsed by 

 their gigantic central earths, as appears to be the case with some other 

 stars such as Algol and omicron Ceti. 



The discovery is wonderful, if true, but seems almost incredible ! 

 The proper motions of these two stars have been known for ninety 

 years to be upwards of one second annually, and have all this time been 

 supposed to be rectilinear, or nearly so, and, therefore, moved in that 

 time between one and tvvo minute;. ; and if this time and distance be 

 necessary before the curvature could be detected, what must be the size 

 of the curve and the length of the period ? Several degrees, perhaps, 

 and thousands of years in one revolution. The binary stars offer noth- 

 ing so gigantic as this. The longest period yet discovered is that of 

 gamma Leonis, 1200 years. Gamma Virginis has a period of more than 

 600 years, and a major s. a. of ellipse of only 12", which, at the usual 

 distance assigned to the stars, would give an orbit double that of Uranus 

 — what then will be the size of an orbit in which ten times this distance 

 can be just distinguished from a straight line, and what must be the size 

 of a central body that can hold Sirius iu check at such a distance ^ How 

 eagerly may we look for further particulars. 



There are some curious considerations connected with the distance 

 and proper motions of the fixed stars, which I do not think have been 

 noticed. It has generally been supposed that the stars are as far from 

 each other as from the solar system, but this cannot always be true, for 

 two stars equally distant from each other, and from the earth, must be 

 separated by an arc of 60°, yet many stars of the first magnitude are 

 much nearer than this ; Castor and Pollux are but 5° apart, Sirius and 

 Procyon less than 15°, and many stars of the second magnitude have 

 still smaller intervals ; they must, theiefore, be much nearer to eacli oth- 

 er than to the earth, and if so, why may we not look to sec them aflect- 

 9 ■ /' 



